Polymeric laminates, processes for producing the same, and use thereof

ABSTRACT

The present invention relates to a laminated membrane comprising a membrane (I) which comprises aromatic polymer electrolyte containing a super strong acid group and a membrane (II) which comprises one compound selected from the group consisting of electrolytes of perfluoroalkylsulfonic acid polymer and non-super strong acid polymer, and a laminated membrane comprising a membrane (III) which comprises a perfluoroalkylsulfonic acid polymer electrolyte and a membrane (IV) which comprises a non-super strong acid polymer electrolyte. The laminated membrane of the present invention is an electrolyte membrane excellent in generation performance and excellent also in the respect of mechanical strength.

FIELD OF THE INVENTION

The present invention relates to an electrolyte membrane, morespecifically, a laminated membrane of a polymer electrolyte.

BACKGROUND OF THE TECHNOLOGY

Electrolyte membranes are used as a barrier membrane in anelectrochemical device such as primary batteries, secondary batteries,solid polymer type fuel cells and the like. For example, aliphaticpolymer electrolyte membranes having a perfluoroalkylsulfonic acid as asuper strong acid in a side chain and a perfluoroalkyl in its main chainare conventionally used mainly because of excellent properties of a fuelcell. However, such a polymer membrane has a problem that it is deformeddue to pressure applied to the surface of a cell in a fuel cell, andimprovement in mechanical strength is desired.

Recently, development of inexpensive electrolyte membranes substitutablefor the above-mentioned electrolyte membrane is being activated. Amongothers, polymer electrolyte membranes obtained by introducing a sulfonicacid group into an aromatic polyether being excellent in heat resistanceand having high film strength, namely, aromatic polymer electrolytemembranes having a sulfonic group and having an aromatic main chain arepromising, and for example, polymer electrolyte membranes made ofsulfonated polyether ketone (Japanese Patent Application NationalPublication (Laid-Open) No. 11-502249), sulfonated polyether sulfone(Japanese Patent Application Laid-Open (JP-A) Nos. 10-45913, 10-21943)and the like are suggested.

However, fuel cells using these electrolyte membranes are notsufficiently satisfactory in the respects of power generation propertyand the like and there is a desire for improvement in an electrolytemembrane.

SUMMARY OF THE INVENTION

The present inventors have intensively studied for solving theabove-mentioned problems of conventional electrolyte membranes andresultantly found that a laminated membrane obtained by laminating amembrane comprising a specific polymer electrolyte and a membranecomprising other polymer electrolyte can attain the object and showsexcellent properties as a proton conductive membrane of a fuel cell andthe like, further, variously investigated to complete the presentinvention.

Namely, the present invention relates to a laminated membrane comprisinga membrane (I) which comprises aromatic polymer electrolyte containing asuper strong acid group and a membrane (II) which comprises oneelectrolyte selected from the group consisting of electrolytes ofperfluoroalkylsulfonic acid polymer and non-super strong acid polymer,and a laminated membrane comprising a membrane (III) which comprises aperfluoroalkylsulfonic acid polymer electrolyte and a membrane (IV)which comprises a non-super strong acid polymer electrolyte.

Further, the present invention provides a method of producing both theabove-mentioned laminated membranes and a use thereof.

PREFERABLE MODES FOR CARRYING OUT THE INVENTION

The present invention will be illustrated in detail below.

One aspect of the laminated membrane of the present invention is alaminated membrane comprising a membrane (I) which comprises aromaticpolymer electrolyte containing a super strong acid group and a membrane(II) which comprises one electrolyte selected from the group consistingof electrolytes of perfluoroalkylsulfonic acid polymer and non-superstrong acid polymer.

In the present invention, the non-super strong acid polymer electrolyteor perfluoroalkylsulfonic acid polymer electrolyte is a polymerelectrolyte having an ion exchange group and containing no super strongaid group, and examples of the ion exchange group of the electrolyteinclude cation exchange groups such as —SO₃H, —COOH, —PO(OH)₂, —POH(OH),—SO₂NHSO₂—, -Ph(OH) (Ph represents a phenyl group) and the like, andanion exchange groups such as —NH₂, —NHR, —NRR′, —NRR′R″⁺. —NH₃ ⁺ andthe like (R represents an alkyl group, cycloalkyl group, aryl group andthe like), and the like. The ion exchange groups may partially ortotally form salt(s) with counter ion(s).

Examples of the non-super strong acid polymer electrolyte include (A)polymer electrolytes as a polymer having a main chain of an aliphatichydrocarbon and a sulfonic group and/or phosphonic group are/isintroduced; (B) polymer electrolytes as a polymer of an aliphatichydrocarbon in which hydrogen atoms in a main chain are partiallysubstituted with fluorine and a sulfonic group and/or phosphonic groupare/is introduced; (C) polymer electrolytes as a polymer having a mainchain containing an aromatic ring and a sulfonic group and/or phosphonicgroup are/is introduced; (D) polymer electrolytes as a polymer such aspolysiloxane, polyphosphazene and the like containing substantially nocarbon atom in a main chain and a sulfonic group and/or phosphonic groupare/is introduced; (E) polymer electrolytes as a copolymer containing oftwo or more repeating units selected from repeating units constitutingpolymers before introduction of a sulfonic group and/or phosphonic groupof (A) to (D) and the polymer carrying a sulfonic group and/orphosphonic group are/is introduced; (F) polymer electrolytes containinga nitrogen atom in its main chain or side chain, and an acidic compoundsuch as sulfuric acid, phosphoric acid and the like is introduced by ionbond; and the like.

Examples of the above-mentioned polymer electrolyte (A) includepolyvinylsulfonic acid, polystyrenesulfonic acid,poly(α-methylstyrene)sulfonic acid and the like.

As the above-mentioned polymer electrolyte (B), there are mentionedsulfonic acid type polystyrene-graft-(ethylene-tetrafluoroethylene)copolymers constituted of a main chain and a hydrocarbon side chain,wherein the main chain is produced by copolymerization of a hydrocarbonfluorine vinyl monomer and a hydrocarbon vinyl monomer and thehydrocarbon side chain has a sulfonic group (ETFE, for example, JP-A No.9-102322). As the above-mentioned polymer electrolyte (B), there arementioned sulfonic acid type poly(trifluorostyrene)-graft-ETFE membranesobtained by graft-polymerizing α,β,β-trifluorostyrene to a membrane madeof a copolymer of a hydrocarbon fluorine vinyl monomer and hydrocarbonvinyl monomer, and introducing a sulfonic group into this to give asolid polymer electrolyte membrane (for example, U.S. Pat. Nos.4,012,303 and No. 4,605,685), and the like.

The above-mentioned polymer electrolyte (C) may be that of which mainchain contains a hetero atom such as an oxygen atom and the like, andexamples thereof include those obtained by introducing a sulfonic groupinto a homo-polymer such as polyether ether ketone, polysulfone,polyether sulfone, poly(arylene ether), polyimide,poly((4-phenoxybenzoyl)-1,4-phenylene), polyphenylenesulfide,polyphenylquinoxalene and the like, and sulfoarylated polybenzimidazole,sulfoalkylated polybenzimidazole, phosphoalkylated polybenzimidazole(for example, JP-A No. 9-110982), phosphonated poly(phenylene ether)(for example, J. Appl. Polym. Sci., 18, 1969 (1974)) and the like.

As the above-mentioned polymer electrolyte (D), there are listed, forexample, that which is obtained by introducing a sulfonic group intopolyphosphazene, polysiloxane having a phosphonic group described inPolymer Prep., 41, No. 1, 70 (2000), and the like.

The above-mentioned polymer electrolyte (E) may be that obtained byintroducing a sulfonic group and/or phosphonic group into a randomcopolymer, that obtained by introducing a sulfonic group and/orphosphonic group into an alternating copolymer, or that obtained byintroducing a sulfonic group and/or phosphonic group into a blockcopolymer. As that obtained by introducing a sulfonic group into arandom copolymer, there are listed, for example, sulfonated polyethersulfone-dihydroxybiphenyl copolymers (for example, JP-A No. 11-116679).

As the above-mentioned polymer electrolyte (F), there are listed, forexample, polybenzimidazole containing phosphoric acid described inJapanese Patent Application National Publication (Laid-Open) No.11-503262, and the like.

As specific examples of the block having a sulfonic group and/orphosphonic group in the block copolymer contained in the above-mentionedpolymer electrolyte (E), there are listed, for example, blocks having asulfonic group and/or phosphonic group described in JP-A No.2001-250567.

On the other hand, as the perfluoroalkylsulfonic acid polymerelectrolyte, there are mentioned (B′) polymer electrolytes as a polymerof an aliphatic hydrocarbon in which hydrogen atoms in a main chain aretotally substituted with fluorine and a sulfonic group and/or phosphonicgroup are/is introduced, and examples thereof include polymers having aperfluoroalkylsulfonic acid as a side chain and a perfluoroalkyl as amain chain typified by Nafion (trade mark of DuPont, the same as below).

The weight-average molecular weight of the perfluoroalkylsulfonic acidpolymer electrolyte or non-super strong acid polymer electrolyte used inthe present invention (hereinafter, referred to as polymer electrolytein some cases) is usually about 1000 to 1000000, and the equivalentweight of ion exchange group is usually about 500 to 5000 g/mol.

Among the above-mentioned non-super strong acid polymer electrolytes (A)to (F), the polymer electrolytes (C) as a polymer having a main chaincontaining an aromatic ring and a sulfonic group and/or phosphonic groupare/is introduced, are preferably used.

The membrane made of a perfluoroalkylsulfonic acid polymer electrolyteor non-super strong acid polymer electrolyte used in the presentinvention (hereinafter, referred to as polymer electrolyte membrane insome cases) is usually composed of a polymer electrolyte as describedabove, and as the production method, for example, a solvent cast methodand the like can be used. Specifically, a polymer electrolyte membranecan be produced by applying a solution of a polymer electrolyte asdescribed above on a base material to form a layer, then, removing asolvent.

Here, the base material is not particularly restricted providing it hasresistance to a solvent and the membrane can be peeled after membraneformation, and usually, glass plates, PET (polyethylene terephthalate)films, stainless plates, stainless belts, silicon wafers and the likeare used.

These base materials may be, if necessary, subjected to a releasingtreatment, emboss processing or delustering processing on its surface.The thickness of a polymer electrolyte membrane is not particularlyrestricted and preferably from 10 to 300 μm. Thickness of larger than 10μm is preferable for obtaining the thickness of a membrane which canpractically use, and for decrease in membrane resistance, namely, forimprovement in performance of generating electricity, thickness ofsmaller than 300 μm is preferable. Such membrane thickness can becontrolled by the concentration of a solution or application thicknesson a base material.

A solution of a polymer electrolyte is usually prepared by using asolvent capable of dissolving the above-mentioned polymer electrolyteand thereafter capable of being removed. As such a solvent, for example,aprotic polar solvents such as N,N-dimethylformamide,N,N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide andthe like, chlorine solvents such as dichloromethane, chloroform,1,2-dichloroethane, chlorobenzene, dichlorobenzene and the like,alcohols such as methanol, ethanol, propanol and the like, alkyleneglycol monoalkyl ethers such as ethylene glycol monomethyl ether,ethylene glycol monoethyl ether, propylene glycol monomethyl ether,propylene glycol monoethyl ether and the like, are preferably used.These can be use singly, and if necessary, two or more solvents can alsobe used in admixture. Of them, dimethylacetamide, methylenechloride-methanol mixed solvent, dimethylformamide, dimethyl sulfoxideare preferable due to high solubility.

As the application method, a spray method may be used, and, a bar coatermethod and spin coater method are preferable since a uniform layer canbe formed, and particularly, a spin coater is further preferably usedsince a uniform thin layer can be formed.

The super strong acid group-containing aromatic polymer electrolyte usedin the present invention is an electrolyte of an aromatic polymer havinga super strong acid group, and a super strong acid group may exist in aside chain or main chain.

Here, the aromatic polymer means a polymer having a main chainconstituted mainly of an aromatic ring, for example, a mono-cyclicaromatic ring such as benzene or the like, poly-cyclic aromatic ringsuch as naphthalene, biphenyl or the like, hetero-cyclic aromatic ringsuch as pyridine or the like, poly-cyclic hetero-cyclic aromatic ringsuch as benzimidazole or the like.

Such a polymer is not particularly restricted providing its main chainis constituted mainly of an aromatic ring, and for example, polymerssuch as polyphenylene ether, polynaphthylene, polyphenylene,polyphenylene sulfide, polyether ether ketone, polyether ether sulfone,polysulfone, polyether sulfone, polyether ketone, polybenzimidazole,polyimide and the like are listed. Of them, preferably listed arepolymers such as polyphenylene ether, polyphenylene, polyether ketone,polyether ether ketone, polyether ether sulfone, polyether sulfone andthe like.

An aromatic ring in these polymers may have a substituent in addition toa super strong acid group, and examples of such a substituent includealkyl groups having 1 to 6 carbon atoms such as a hydroxyl group, methylgroup, ethyl group, propyl group and the like, alkoxy groups having 1 to6 carbon atoms such as a methoxy group, ethoxy group and the like,aralkyl groups having 7 to 12 carbon atoms such as a benzyl group andthe like, aryl groups such as a phenyl group, naphthyl group and thelike, halogens such as a fluorine atom, chlorine atom, bromine atom andthe like. A plurality of substituents may be present, and in this case,these may be different. Among others, those substituted with a fluorineatom are preferable.

When the super strong acid group-containing aromatic polymer electrolyteis an aromatic polymer having a super strong acid group in a side chain,its main chain is an aromatic polymer as described above, and a superstrong acid group is present in a side chain. Here, the super strongacid group means an acid substantially stronger than 100% sulfuric acid.

Examples of such a super strong acid group include groups of thefollowing general formulae (2a) to (2d).-G-SO₃ ⁻W⁺  (2a)-G-SO₂N⁻W⁺SO₂-E  (2b)-G-P(O)(O⁻W⁺)₂  (2c)-G-P(O)O⁻W⁺-E  (2d)(wherein, G represents an alkylene group of which hydrogen atoms arepartially or totally substituted with fluorine, aralkylene group ofwhich hydrogen atoms are partially or totally substituted with fluorineor arylene group of which hydrogen atoms are partially or totallysubstituted with fluorine, W⁺ represents a cation, E represents an alkylgroup of which hydrogen atoms are partially or totally substituted withfluorine, aralkyl group of which hydrogen atoms are partially or totallysubstituted with fluorine or aryl group of which hydrogen atoms arepartially or totally substituted with fluorine.).

Typical examples of W⁺ include a hydrogen ion, and alkali metal ionssuch as a sodium ion, lithium ion and the like. When used for fuelcells, a hydrogen ion is preferable.

The alkylene group G usually has about 1 to 6 carbon atoms, thearalkylene group G usually has about 7 to 12 carbon atoms, and thearylene group G usually has about 6 to 10 carbon atoms. Of them, G ispreferably an alkylene group of which hydrogen atoms are totallysubstituted with fluorine, aralkylene group of which hydrogen atoms aretotally substituted with fluorine or arylene group of which hydrogenatoms are totally substituted with fluorine. Preferable examples of Ginclude a difluoromethylene group, tetrafluoroethylene group,hexafluoropropylene group, hexafluorobenzylene group,tetrafluorophenylene group, hexafluoronaphthylene group and the like.

The alkyl group E usually has about 1 to 6 carbon atoms, the aralkylgroup E usually has about 7 to 12 carbon atoms, and the aryl group Eusually has about 6 to 10 carbon atoms. Of them, E is preferably analkyl group of which hydrogen atoms are totally substituted withfluorine, aralkyl group of which hydrogen atoms are totally substitutedwith fluorine or aryl group of which hydrogen atoms are totallysubstituted with fluorine. Preferable examples of E include atrifluoromethyl group, pentafluoroethyl group, heptafluoropropyl group,heptafluorobenzyl group, pentafluorophenyl group, heptafluoronaphthylgroup and the like.

Preferable examples of the above-mentioned super strong acid group (2a)include groups of the following formulae L-1 to L-5.

Preferable examples of the above-mentioned super strong acid group (2b)include groups of the following formulae L-6 to L-30.

Preferable examples of the above-mentioned super strong acid group (2c)include groups of the following formulae L-31 to L-35.

Preferable examples of the above-mentioned super strong acid group (2d)include groups of the following formulae L-36 to L-60.

Among L-1 to L-60 as described above, L-1 to L-30 are preferably used.

Examples of aromatic polymers having a super strong acid group asdescribed above in a side chain include polymers containing a structureof the following general formula (1).-(A-Z)_(m)-(A′-Z′)_(n)-  (1)(wherein, A represents a divalent aromatic group and A′ represents adivalent aromatic group on which super strong acid group has beensubstituted. Z, Z′ represent each independently a direct bond ordivalent group. m and n represent the number of repeating units, n is inthe range of 10 to 100000, n repeating units may be the same as ordifferent from each other, and m is in the range of 0 to 100000, mrepeating units may be the same as or different from each other.).

Here, A represents a divalent aromatic group, and examples thereofinclude divalent aromatic groups selected from the following formulae(3a) to (3c).

(wherein, R represents a hydroxyl group, alkyl group having 1 to 6carbon atoms, alkoxy group having 1 to 6 carbon atoms, aralkyl grouphaving 7 to 12 carbon atoms, aryl group or halogen. p, r, s and trepresent each independently a number of from 0 to 4, and q represents anumber of from 0 to 6, and when there are a plurality of Rs, these maybe the same or different. j represents a number of 0 or 1. Y represent adirect bond or divalent group, and when there are a plurality of Ys,these may be the same or different.).

Examples of the alkyl group R having 1 to 6 carbon atoms include amethyl group, ethyl group, propyl group and the like, examples of thealkoxy group R having 1 to 6 carbon atoms include a methoxy group,ethoxy group and the like, examples of the aralkyl group R having 7 to12 carbon atoms include a benzyl group, toluyl group and the like,examples of the aryl group include a phenyl group, naphthyl group andthe like, and examples of the halogen include a fluorine atom, chlorineatom, bromine atom and the like.

Y represents a direct bond or divalent group, and specific examples of Yinclude a direct bond, —O—, —S—, —CO—, —SO₂—, alkylene groups having 1to 20 carbon atoms and alkylenedioxy groups having 1 to 20 carbon atoms.Preferable are a direct bond, —O—, —S—, —SO₂—, alkylene groups having 1to 10 carbon atoms and alkylenedioxy groups having 1 to 10 carbon atoms.When there are a plurality of Ys, these may be the same or different.Here, examples of the alkylene group having 1 to 20 carbon atoms includea methylene group, ethylene group, propylene group, butylene group andthe like. Examples of the alkylenedioxy group having 1 to 20 carbonatoms include a methylenedioxy group, ethylenedioxy group and the like.

A′ in the formula (1) represents a divalent aromatic group havingsubstitution of a super strong acid group, and typical examples thereofinclude divalent aromatic groups selected from the following formulae(3d) to (3g).

(wherein, R represents a hydroxyl group, alkyl group having 1 to 6carbon atoms, alkoxy group having 1 to 6 carbon atoms, aralkyl grouphaving 7 to 12 carbon atoms, aryl group or halogen. Z″ and Y representeach independently a direct bond or divalent group, and when there are aplurality of Z′s, these may be the same or different, and when there area plurality of Ys, these may be the same or different. D represents asuper strong acid group, and when there are a plurality of Ds, these maybe the same or different. h, h″ and h′″ represent each independently anumber of from 1 to 4, h′ represents a number of from 1 to 6, (p′+h),(r′+h″) and (s″+h′″) represent each independently a number of from 1 to4, s′, t′, r″ and t″ represent each independently a number of from 0 to4, (q′+h′) represents a number of from 1 to 6, when there are aplurality of Rs, these may be the same or different. j represents anumber of 0 or 1. ).

Here, R and Y are the same as described for A. D represents a superstrong acid group, and such super strong acid group includes superstrong acid groups selected from the above-mentioned (2a) to (2d). Z″represents a direct bond or divalent group, and specific examples of Z″include alkylene groups having about 1 to 20 carbon atoms substitutedwith fluorine, alkylenedioxy groups having about 1 to 20 carbon atomssubstituted with fluorine, arylene groups having about 6 to 12 carbonatoms optionally substituted with fluorine, aryleneoxy groups havingabout 6 to 12 carbon atoms optionally substituted with fluorine andalkyleneoxy groups having about 1 to 20 carbon atoms optionallysubstituted with fluorine, in addition to the same divalent groups asmentioned for Y such as a direct bond, —O—, —S—, —CO—, —SO₂—, alkylenegroups having 1 to 20 carbon atoms and alkylenedioxy groups having 1 to20 carbon atoms.

Preferably mentioned are a direct bond, —O—, —S—, —SO₂—, alkylene groupshaving 1 to 10 carbon atoms, alkylenedioxy groups having 1 to 10 carbonatoms, alkylene groups having 1 to 10 carbon atoms substituted withfluorine, alkylenedioxy groups having 1 to 10 carbon atoms substitutedwith fluorine, arylene groups having 6 to 10 carbon atoms optionallysubstituted with fluorine, aryleneoxy groups having 6 to 10 carbon atomsoptionally substituted with fluorine and alkyleneoxy groups having 1 to10 carbon atoms optionally substituted with fluorine.

Here, examples of the alkylene group having 1 to 20 carbon atoms includea methylene group, ethylene group, propylene group, butylene group andthe like. Examples of the alkylenedioxy group having 1 to 20 carbonatoms include a methylenedioxy group, ethylenedioxy group and the like.Examples of the alkylene group having about 1 to 20 carbon atomssubstituted with fluorine include a difluoromethylene group,tetrafluoroethylene group, hexafluoropropylene group andoctafluorobutylene group. Examples of the alkylenedioxy group having 1to 20 carbon atoms substituted with fluorine include a2,2,3,3-tetrafluorobutylenedioxy group,2,2-bis(trifluoromethyl)propylenedioxy group and the like. Examples ofthe arylene group having about 6 to 12 carbon atoms optionallysubstituted with fluorine include a phenylene group,tetrafluorophenylene group and the like. Examples of the aryleneoxygroup having about 6 to 12 carbon atoms optionally substituted withfluorine include a phenyleneoxy group, tetrafluorophenyleneoxy group andthe like. Examples of the alkyleneoxy group having about 1 to 20 carbonatoms optionally substituted with fluorine include a methyleneoxy group,difluoromethyleneoxy group, ethyleneoxy group, tetrafluoroethyleneoxygroup and the like.

Z, Z′ in the formula (1) represent each independently a direct bond ordivalent group, and mentioned as Z, Z′ are the same divalent groups asthose described for Y. m, n represent the number of repeating units, nis usually in the range of 10 to 100000, n repeating units may be thesame as or different from each other. m is usually in the range of 0 to100000, m repeating units may be the same as or different from eachother. n is preferably 15 or more, more preferably 20 or more. n ispreferably 50000 or less, more preferably 10000 or less. m is preferably50000 or less, particularly preferably 10000 or less. n repeating unitsand m repeating units may take any bonding mode of a block copolymer,random copolymer, alternating copolymer, multi-block copolymer or graftcopolymer.

The number-average molecular weight of an aromatic polymer having asuper strong acid group in a side chain is usually 5000 to 500000,preferably 10000 to 300000, particularly preferably 15000 to 100000.

An aromatic polymer having a super strong acid group in a side chain asdescribed above can be obtained, for example, by reacting an aromaticpolymer of the following general formula (7):-(A-Z )_(m)-(A″-Z′)_(n-)  (7)with a moiety of the following general formula (8)E-D  (8)

In the formula (7), A, Z, Z′, m and n have the same meanings asdescribed above, and A″ represents a divalent aromatic group obtained bysubstituting a super strong acid group substituted in A′ described abovewith a hydrogen atom. Examples of A″ include groups selected from thefollowing general formulae (4a) to (4d).

(In the above-mentioned formulae, R, Y, p′, q′, r′, s′, t′, r″, s″, t″,h, h′, h″, h′″ and j have the same meanings as described above, and Z′″represents a functional group.).

Here, the functional group includes halogens, hydroxyl group, nitrogroup, amino group, carboxyl group, carboxylic halide group, sulfonicgroup, sulfonic halide group, alkylene halide group, hydroxylalkylene,aryl group and the like, and preferably are halogens and hydroxyl group,and particularly preferable are halogens. As the halogen, chloro, bromoand iodo are preferable.

In the formula (8), D has the same meaning as described above, Erepresents a group which can form a direct bond or divalent groupbonding an aromatic ring with a super strong acid group by a reaction.

The above-mentioned method is not particularly restricted, and forexample a combination of, a halogen E and a halogen Z′″ are reacted inthe presence of a metal to form a direct bond, and other methods arementioned. Mentioned as the halogen are fluorine, chlorine, bromine andiodine, and preferably mentioned are chlorine, bromine and iodine.Generally, the reaction can be conducted even under a condition using nosolvent, and preferably, this reaction is conducted in a suitablesolvent. As the solvent, hydrocarbon solvents, ether solvents, ketonesolvents, amide solvents, sulfone solvents, sulfoxide solvents and thelike can be used. Tetrahydrofuran, diethyl ether, dimethyl sulfoxide,sulfolane, N,N-dimethylformamide, N,N-dimethylacetamide,N-methylpyrrolidone, N,N′-dimethylimidazolidinone and the like arepreferably used. As the metal, copper, sodium, lithium, potassium, zinc,iron, chromium, nickel, magnesium and the like are mentioned, andpreferable are copper, zinc and sodium. The amount of a metal used is ½equivalent or more of the sum of an alkyl halide and/or aryl halide. Thereaction temperature is preferably from about −10° C. to about 25° C.,more preferably from about 0° C. to about 200° C.

An aromatic polymer represented by the general formula (7) and having,for example, Z′″ can be obtained by a method of introducing Z′″ into anaromatic polymer by a polymer reaction, or other methods.

Mentioned as this method are, for example, a method of introducingbromine by reacting N-bromosuccinimide, a method of introducing ahalogen by directly acting a chlorine gas, bromine, iodine and the like,a method of converting a hydroxyl group into bromine with phosphorustribromide, a method of converting a hydroxyl group into chlorine withthionyl chloride, and the like (McMurray Organic Chemistry (firstvolume), pp. 291 to 296, Tokyo Kagaku Dojin, 1992).

The aromatic polymer into which Z′″ is introduced by a polymer reactionis not particularly restricted providing its main chain is constitutedmainly of an aromatic ring, and examples thereof include polymers suchas polyphenylene ether, polynaphthylene, polyphenylene, polyethersulfone, polyphenylene sulfide, polyether ether ketone, polyether ethersulfone, polysulfone, polyether sulfone, polyether ketone,polybenzimidazole and the like. Of them, polyphenylene ether,polynaphthylene, polyphenylene and polyether sulfone polymers arepreferably used. These polymers may be a copolymer composed of any twoor more polymers such as a block copolymer, random copolymer,alternating copolymer, multi-block copolymer, graft copolymer and thelike.

These polymers are available from makers such as Aldrich, SumitomoChemical Co., Ltd. and the like. For example, polyether sulfonescommercially available under trade names of SUMIKA EXCEL PES 3600 P, PES4100 P, PES 4800 P, PES 5200 P, PES 5003 P (all are trade marks ofSumitomo Chemical Co., Ltd., applicable also in the followings) can beobtained from Sumitomo Chemical Co., Ltd.

When the super strong acid group-containing aromatic polymer electrolyteis an aromatic polymer having a super strong acid group in its mainchain, the main chain is an aromatic polymer as described above, and themain chain has further a super strong acid group. As the aromaticpolymer having a super strong acid group in its main chain, examples arepolymers having a polymerization unit of the following formula (4):—[Ar¹—(SO₂—N⁻(X⁺)—SO₂—Ar²)_(a)—SO₂—N—(X⁺)—SO₂—Ar¹—O]—  (4)(wherein, Ar¹, Ar² represent each independently a divalent aromaticgroup optionally having a substituent, a represents an integer of 0 to3, and X⁺ represents an ion selected from a hydrogen ion, alkali metalions and ammonium.).

Ar¹, Ar² in the formula (4) represent each independently a divalentaromatic group optionally having a substituent, and examples of thedivalent aromatic group optionally having a substituent include thefollowing groups:

(wherein, R¹ represents a hydrocarbon group having 1 to 10 carbon atoms,hydrocarbonoxy group having 1 to 10 carbon atoms, acetyl group, benzoylgroup, nitrile group, sulfonic group, carboxyl group, phosphonic groupor halogen atom, a represents an integer of 0 to 4, and b, c representan integer of 0 to 4, the sum of b and c is being an integer of 0 to 6.When there are a plurality of R¹s, these may be the same or different. Yrepresents a direct bond, —O—, —S—, —C(O)—, —SO₂— or —C(R³)₂—. R³represents a hydrogen atom, hydrocarbon group having 1 to 10 carbonatoms, halogenated hydrocarbon group having 1 to 10 carbon atoms, andtwo R³S may be the same or different and may form a ring. When there area plurality of Ys, these may be the same or different.).

Here, examples of the hydrocarbon group having 1 to 10 carbon atomsinclude a methyl group, ethyl group, propyl group, phenyl group,naphthyl group and the like. Examples of the hydrocarbonoxy group having1 to 10 carbon atoms include a methoxy group, ethoxy group, phenoxygroup and the like. As the halogen atom, fluorine, chlorine and bromineare mentioned.

As the halogenated hydrocarbon group R³ having 1 to 10 carbon atoms, atrifluoromethyl group and the like are listed. As those in which two R³sform a ring, for example, a cyclohexane ring, fluorene ring and the likeare listed.

The degree of ion dissociation of a disulfonylimide group variesdepending on adjacent aromatic groups, or substituents on Ar¹ and Ar²,and when an electron attractive property of a substituent is higher,degree of ion dissociation is higher. Therefore, preferable Ar¹, Ar² arethose substituted with a substituent having a high electron attractiveproperty, for example, those having substitution of a halogen atom, andmore preferable are those having substitution of a fluorine atom. Amongothers, it is preferable that Ar¹, Ar² represent tetrafluorophenylenesince the degree of ion dissociation of a disulfonylimide group is high.

As X⁺, a hydrogen ion, alkali metal ions and ammonium ion are listed,and when a laminated membrane is used in a fuel cell, it is desirablethat X⁺ is a hydrogen ion.

An aromatic polymer having a super strong acid group in its main chaincomprises a polymerization unit of the formula (4) and a polymerizationunit other than this, and may be an alternating copolymer, randomcopolymer or block copolymer.

As the preferably polymerization unit other than the polymerizationunit-of the formula (4), for example, a polymerization unit of thefollowing formula (5), and the like are mentioned. Further, in additionto the polymerization unit of the formula (5), a polymerization unitother than this may be contained, and such a polymerization unit is notparticularly restricted, and for example, a polymerization units of thefollowing formula (6), and the like are mentioned.—[Ar³—O]—  (5)—[Ar⁴—O]—  (6)(wherein, Ar³, Ar⁴ represent each independently a divalent aromaticgroup optionally having a substituent.).

Here, as the divalent aromatic group optionally having a substituent,for example, the same groups as described above are mentioned.

Polymers having a polymerization unit of the above-mentioned formulae(4) and (5) can be produced by using, for example, a compound of thefollowing formula (9), an aromatic diol of the following general formula(10), and the like as raw materials and polymerizing them.Z-Ar¹—(SO₂—N⁻(X⁺)—SO₂—Ar²)_(a)—SO₂—N⁻(X⁺) —SO₂—Ar¹-Z  (9)HO—Ar³—OH  (10)(wherein, Ar¹, Ar², Ar³, a and X⁺ have the same meanings as describedabove, and Z represents a halogen atom or a nitro group).

Here, as the halogen atom, fluorine, chlorine, bromine and the like arementioned. Preferable are fluorine and chlorine, and more preferable isfluorine.

Typical examples of the aromatic diol (10) include hydroquinone,resorcinol, catechol, 2-methylhydroquinone, 2,6-dimethylhydroquinone,2-methoxyhydroquinone, 2-phenylhydroquinone, 2,6-diphenylhydroquinone,2-sulfohydroquinone, 2,6-disulfohydroquinone, 2-methylresorcinol,2,4-dimethylresorcinol, 2-phenylresorcinol, 2,4-diphenylresorcinol,1,2-dihydroxynaphthalene, 1,4-dihydroxynaphthalene,1,5-dihydroxynaphthalene, 2,6-dihydroxynaphthalene,2,7-dihydroxynaphthalene, 6,7-dihydroxy-2-naphthalenesulfonic acid,2,7-dihydroxynaphthalene-3,6-disulfonic acid,4,5-dihydroxynaphthalene-2,7-disulfonic acid, 4,4′-dihydroxybiphenyl,4,4′-dihydroxy-3,3′-disulfobiphenyl,4,4′-dihydroxy-3,3′-diphenylbiphenyl, 2,4′-dihydroxybiphenyl,2,2′-dihydroxybiphenyl, 4,4′-dihydroxydiphenylmethane,1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)propane,2,2-bis(4-hydroxyphenyl)butane, 1,1-bis(4-hydroxyphenyl)cyclohexane,2,2-bis(4-hydroxyphenyl)-1,1,1,3,3,3-hexafluoropropane,1,1-bis(4-hydroxyphenyl)-1-phenylethane,bis(4-hydroxyphenyl)diphenylmethane, 9,9-bis(4-hydroxyphenyl)fluorene,4,4′-dihydroxydiphenyl ether, bis(4-hydroxyphenyl) sulfide,bis(3,5-dimethyl-4-hydroxyphenyl) sulfide, 4,4′-dihydroxybenzophenone,4,4′-dihydroxydiphenylsulfone,4,4′-dihydroxy-3,3′-disulfodiphenylsulfone,bis(3,5-dimethyl-4-hydroxyphenyl)sulfone, and alkali metal salts thereof(sodium salt, potassium salt), and the like. Two or more of them canalso be used.

Of them, hydroquinone, 4,4′-dihydroxybiphenyl,2,2-bis(4-hydroxyphenyl)propane, 4,4′-dihydroxy-3,3′-diphenylbiphenyl,4,4′-dihydroxydiphenyl ether, and alkali metal salts thereof, and thelike have high reactivity and used preferably.

A compound of the formula (9) which is another raw material can beproduced as described below.

That in which a=0 can be produced easily by, for example, reactingZ-Ar¹—SO₂Cl which is a corresponding sulfonyl chloride compound withZ-Ar¹—SO₂NH₂ which is a sulfoneamide compound. Usually, a base in anamount of 2-fold equivalent or more is added to the system and they arereacted in a solvent while controlling the pH value in the system at 7to 8.

As the solvent, for example, acetone, 2-butanone, tetrahydrofuran,1,4-dioxane, acetonitrile, N,N-dimethylacetamide, N,N-dimethylformamide,dimethyl sulfoxide, and a mixture of two or more of them, and the likeare used. As the base, sodium hydride, lithium hydride, triethylamine,pyridine, dimethylaminopyridine and the like are used. The reactiontemperature is preferably from about 0° C. to about 150° C., morepreferably from about 20° C. to about 80° C. The reaction time isusually from about I hour to about 20 hours.

The sulfoneamide compound used here can be produced by reactingZ-Ar¹—SO₂Cl which is a corresponding sulfonyl chloride compound withammonia or ammonium chloride in the presence of a base in an amount oftwo-fold equivalent or more.

Among compounds of the formula (10), that in which m=l can be producedeasily, for example, by reacting Z-Ar¹—SO₂NH₂ which is a sulfoneamidecompound with ClSO₂—Ar²—SO₂Cl which is a bissulfonyl chloride compound,or reacting Z-Ar¹—SO₂Cl which is a sulfonyl chloride compound withNH₂SO₂—Ar²—SO₂NH₂ which is a bissulfoneamide compound. The reaction is,when m=0 for example, carried out under the same conditions. Thebissulfoneamide compound used here can be produced by reacting acorresponding bissulfonyl chloride compound with ammonia or ammoniumchloride and the like.

Among compounds of the formula (10), that in which a is 2 or 3 can beproduced, for example, by reacting a bissulfonyl chloride compound andbissulfoneamide compound with a sulfonyl chloride compound orsulfoneamide compound in a ternary system. The chain length of anoligomer can be controlled depending on the molar ratio of them,however, it is preferable to use a compound (3) in which a=0 or a=1since, when a is 2 or 3, distribution occurs in chain length,purification at a stage of a compound (10) is difficult in many cases,and the molecular weight of the final polymer may not be increasedeasily in some cases.

Typical examples of the sulfonyl chloride compound used in producing acompound (10) include 4-fluorobenzenesulfonyl chloride,3-fluorobenzenesulfonyl chloride, 2-fluorobenzenesulfonyl chloride,difluorobenzenesulfonyl chloride, trifluorobenzenesulfonyl chloride,tetrafluorobenzenesulfonyl chloride, pentafluorobenzenesulfonylchloride, 4-chlorobenzenesulfonyl chloride, 3-chlorobenzenesulfonylchloride, 2-chlorobenzenesulfonyl chloride, dichlorobenzenesulfonylchloride, trichlorobenzenesulfonyl chloride, 4-bromobenzenesulfonylchloride, 3-bromobenzenesulfonyl chloride, 2-bromobenzenesulfonylchloride, dibromobenzenesulfonyl chloride, 4-nitrobenzenesulfonylchloride, 3-nitrobenzenesulfonyl chloride and the like. Two or more ofthem can also be used. Further, sulfonyl fluoride compounds may also beused instead of these sulfonyl chloride compounds.

Typical examples of the bissulfonyl chloride compound used in producinga compound (10) include, 4-benzenedisulfonyl chloride,1,3-benzenedisulfonyl chloride, 1,2-benzenedisulfonyl chloride,4,4′-biphenyldisulfonyl chloride, naphthalenedisulfonyl chloride and thelike. Two or more of them can also be used. Further, bissulfonylfluoride compounds may also be used instead of these bissulfonylchloride compounds.

The method of polymerizing a compound of the formula (9) and an aromaticdiol of the formula (10) as described above as raw materials is notparticularly restricted, and there are mentioned methods in which, forexample, in the co-presence of an alkali, [1] a compound of the formula(9) and an aromatic diol of the formula (10) are reacted, [2] a compoundof the formula (9), an aromatic diol of the formula (10) and a compoundof the following formula (11) are reacted, [3] a compound of the formula(9) and an aromatic diol of the formula (10) are reacted, then, acompound having a hydroxyl group of the following formula (12) isreacted with the reaction product, [4] a compound of the formula (9) andan aromatic diol of the formula (10) are reacted, then, a compound ofthe following formula (13) is reacted with the reaction product, [5] acompound of the formula (9) and an aromatic diol of the formula (10) arereacted, then, a compound of the following formula (11) and a compoundhaving a hydroxyl group of the following formula (12) are reacted withthe reaction product, [6] a compound of the formula (9) and an aromaticdiol of the formula (10) are reacted, then, an aromatic diol of theformula (10) and a compound of the following formula (13) are reactedwith the reaction product, and the like.W—Ar⁴—W  (11)HO—[Ar⁵—O]_(k)—H  (12)W—[Ar⁶—O]_(k)—Ar⁶—W  (13)(wherein, Ar⁴ has the same meaning as described above, Ar⁵, Ar⁶represent each independently a divalent aromatic group optionally havinga substituent, W represents a halogen atom or nitro group, and krepresents a number of 1 to 5000.).

Here, as the halogen atom, fluorine, chlorine, bromine and the like arementioned.

Typical examples of the compound of the formula (11) include4,4′-difluorobenzophenone, 4,4′-dichlorobenzophenone,2,4-difluorobenzophenone, 4,4′-dibromobenzophenone,3,4′-dinitrobenzophenone, 4,4!-difluorodiphenylsulfone,4,4′-difluoro-3,3′-disulfodiphenylsulfone,4,4-difluoro-3,3′-disulfodiphenylsulfone dipotassium salt,4,4′-difluoro-3,3′-disulfodiphenylsulfone disodium salt,4,4′-dichlorodiphenylsulfone, 4,4-dichloro-3,3′-disulfodiphenylsulfone,4,4′-dichloro-3,3′-disulfodiphenylsulfone dipotassium salt,4,4′-dichloro-3,3′-disulfodiphenylsulfone disodium salt,4,4′-dibromodiphenylsulfone, 4,4′-dinitrodiphenylsulfone,2,6-difluorobenzonitryle, 2,6-dichlorobenzonitryle, hexafluorobenzene,decafluorobiphenyl, octafluoronaphthalene and the like.

Two or more of them can also be used.

Among them, 4,4′-difluorobenzophenone, 4,4′-difluorodiphenylsulfone,4,4′-dichlorodiphenylsulfone, decafluorobiphenyl and the like arepreferably used.

As Ar⁵ in a compound having a hydroxyl group of the formula (12), forexample, the same divalent aromatic groups optionally having asubstituent as described above are mentioned. Ar⁵ may be the same as ordifferent from Ar³, Ar⁴ or the like. Such a compound (12) having ahydroxyl group is not particularly restricted, and examples thereofinclude aromatic polymers such as poly(phenylene ether), poly(etherketone), poly(ether ether ketone), polysulfone, poly(ether sulfone),poly(phenylene sulfide) and the like having a hydroxyl group at theterminal. Two or more of them can also be used.

As Ar⁶ in a compound of the formula (13), for example, the same divalentaromatic groups optionally having a substituent as described above arementioned. Ar⁶ may be the same as or different from Ar³, Ar⁴, Ar⁵ or thelike. Such a compound (13) is not particularly restricted, and examplesthereof include aromatic polymers such as poly(phenylene ether),poly(ether ketone), poly(ether ether ketone), polysulfone, poly(ethersulfone), poly(phenylene sulfide) and the like having a halogen or nitrogroup at the terminal. Two or more of them can also be used.

The number-average molecular weight of the above-mentioned compound (12)or (13) is preferably from 2000 to 50000, more preferably from 5000 to200000, further preferably from 8000 to 100000. When the number-averagemolecular weight is less than 2000, the film strength and heatresistance of a block copolymer may decrease in some cases, and when thenumber-average molecular weight is over 500000, solubility my decreasein some cases.

The polymerization reaction can be carried out according to knownmethods conducted in the presence of an alkali.

As the alkali, known alkalis having polymerization activity can be used.Preferably, alkali metal hydroxides, alkali metal carbonates and thelike are used. Of them, potassium carbonate is suitably used.

The polymerization reaction may be conducted also under a melt conditionusing no solvent, and it is preferably conducted in a solvent. As thesolvent, aromatic hydrocarbon solvents, ether solvents, ketone solvents,amide solvents, sulfone solvents, sulfoxide solvents and the like can beused, and dimethyl sulfoxide, sulfolane, N,N-dimethylformamide,N,N-dimethylacetamide, N-methylpyrrolidone,N,N′-dimethylimidazolidinone, diphenylsulfone and the like arepreferably used.

The reaction temperature of the polymerization reaction is usually fromabout 20° C. to about 300° C., preferably from about 50° C. to about200° C.

Another laminated membrane of the present invention is a laminatedmembrane comprising a membrane (III) which comprises aperfluoroalkylsulfonic acid polymer electrolyte and a membrane (IV)which comprises a non-super strong acid polymer electrolyte. Theperfluoroalkylsulfonic acid polymer electrolyte and non-super strongacid polymer electrolyte used are the same as described above.

By forming a membrane (I) which comprises aromatic polymer electrolytecontaining a super strong acid group as described above, a membrane (I)which comprises aromatic polymer electrolyte containing the super strongacid group can be produced. As this production method, for example, asolvent cast method and the like can be used. Specifically, a method inwhich a solution of an aromatic polymer having a super strong acid groupis applied on a base material to form a layer, then, a solvent isremoved, and the same methods as illustrated for the above-mentionedpolymer electrolyte membrane, are listed.

The laminated membrane of the present invention is obtained bylaminating a membrane (I) which comprises aromatic polymer electrolytecontaining a super strong acid group as described above and a polymerelectrolyte membrane (II) or laminating a membrane (III) which comprisesa perfluoroalkylsulfonic acid polymer electrolyte and a membrane (IV)which comprises a non-super strong acid polymer electrolyte.

A method includes, for example, a method of conjugating a membrane (I)with a membrane (II), a method of applying a solution of an aromaticpolymer having a super strong acid group on a membrane (II) and dryingthis, a method of applying a solution of a polymer electrolyte on amembrane (II) and drying this, a method of immersing a membrane (II) ina solution of an aromatic polymer having a super strong acid group anddrying this, a method of immersing a membrane (I) in a solution of apolymer electrolyte and drying this, and the like.

Of them, the method of applying a solution of a polymer electrolyte on amembrane (II) and drying this is preferably used. As the method ofapplying and drying, the above-mentioned solvent cast method ispreferably used.

When the laminated membrane of the present invention is a laminatedmembrane comprising a membrane (III) which comprises aperfluoroalkylsulfonic acid polymer electrolyte and a membrane (IV)which comprises a non-super strong acid polymer electrolyte, a methodincludes, for example, a method of conjugating a membrane (III) with amembrane (IV), a method of applying a solution of a non-super strongacid polymer electrolyte on a membrane (III) and drying this, a methodof applying a solution of a perfluoroalkylsulfonic acid polymerelectrolyte on a membrane (IV) and drying this, a method of immersing amembrane (III) in a solution of a non-super strong acid polymerelectrolyte and drying this, a method of immersing a membrane (IV) in asolution of a perfluoroalkylsulfonic acid polymer electrolyte and dryingthis, and the like.

Of them, the method of applying a solution of a perfluoroalkylsulfonicacid polymer electrolyte on a membrane (IV) and drying this ispreferably used. As the method of applying and drying, theabove-mentioned solvent cast method is preferably used.

In this method, it is preferable that a halogen solvent such asmethylene chloride, chloroform, 1,2-dichloroethane and the like iscontained as the solvent of a solution of a perfluoroalkylsulfonic acidpolymer electrolyte since then adhesive property of a membrane (III) anda membrane (IV) is enhanced. Further preferable is a methylenechloride/alcohol/water mixed solvent. The content of a halogen solventis preferably 1 wt % or more based on the total amount of the solvent.

Into the above-mentioned solution containing a polymer electrolyte, anaromatic polymer having a super strong acid group or aperfluoroalkylsulfonic acid polymer electrolyte, additives such asplasticizers, stabilizers, releasing agents, water-retaining agents andthe like used in polymers may be added, if necessary. Theabove-mentioned membranes (I) to (IV) can also be used in complex withany porous membranes for the purpose of improving its mechanicalstrength, and the like. Further, for the purpose of improving themechanical strength of these membranes, a method of irradiation ofelectron beam, radiation and the like to cause cross-linking is known,and this method may be used on membranes (I) to (IV) and these laminatedmembranes.

By optionally combining the above-mentioned lamination methods,lamination of three or more layers is also possible. Specifically-listedare a membrane of alternate lamination of three or more layers of (I)and (II), a laminated membrane composed of lamination of two or morekinds of (I), and a layer of (II), a laminated membrane composed oflamination of two or more kinds of (II), and a layer of (I), a laminatedmembrane composed of two or more kinds of (I) layers, and two or morekinds of (II) layers, and laminated membranes combining them, and thelike.

Further, a membrane of alternate lamination of three or more layers of(III) and (IV), a laminated membrane composed of lamination of two ormore kinds of (III), and a layer of (IV), a laminated membrane composedof lamination of two or more kinds of (IV), and a layer of (III), alaminated membrane composed of two or more kinds of (III) layers, andtwo or more kinds of (IV) layers, and laminated membranes combiningthem, and the like are listed.

When the laminated membrane of the present invention is used as anelectrolyte membrane for fuel cells, it is preferable, from theviewpoint of improvement in generation performance, that a membrane (I)constitutes a surface layer on at least one surface, and it is furtherpreferable that it constitutes a surface layer on both surfaces.

In the laminated membrane of the present invention, the laminationamount of a membrane (I) is usually 0.1 wt % to 50 wt %, preferably 0.2wt % to 40 wt %, particularly preferably 0.3 wt % to 30 wt % based onthe total weight of the laminated membrane.

Next, the fuel cell of the present invention will be illustrated.

The fuel cell of the present invention can be produced by connecting anelectrode material carrying a fixed catalyst, as a collector, on bothsurfaces of a laminated membrane.

As the electrode material, known materials can be used, and porouscarbon woven fabric, carbon no-woven fabric or carbon paper arepreferable since they transport a raw material gas to a catalystefficiently.

The catalyst is not particularly restricted providing it can activate aredox reaction of hydrogen and oxygen, and known catalysts can be used,and it is preferable to use fine particles of platinum. Fine particlesof platinum are often carried on carbon in the form of particle or fibersuch as activated carbon, graphite and the like and preferably used.Platinum carried on carbon is mixed with an alcohol solution of aperfluoroalkylsulfonic acid resin to make a paste which is applied on anelectrode material and/or membrane (II) or membrane (III) and dried,constituting efficiently a so-called three-phase interface in whichthree members of the electrode material, polymer electrolyte and fuelgas are in mutual contact, thus, such a procedure is preferably used.Specifically, known methods such as, for example, a method described inJ. Electrochem. Soc.: Electrochemical Science and Technology, 1988, 135(9), 2209, and the like can be used.

EXAMPLES

The following examples will illustrate the present invention furtherspecifically, however, the scope of the invention is not limited tothese examples.

Physical properties in examples and comparative examples were measuredaccording to the following evaluation methods.

[Evaluation Method]

Evaluation of Fuel Cell Properties

A platinum catalyst carried on a carbon was mixed with a lower alcoholsolution (containing 10 wt % water) (manufactured by Aldrich) of Nafion(registered trade mark of Dupont) to give a paste which was applied onporous carbon woven-fabric as an electrode material and dried, to obtaina current collector as an electrode material carrying a fixed catalyst.This current collector was attached on both surfaces of the membrane,obtaining a collector-membrane assembly. A wet oxygen gas was flown toone surface of the connected body and a wet hydrogen gas was flown toanother surface, the connected body was kept at 80° C., and its powergeneration property was measured.

Evaluation of Adhering Property

After evaluation of the fuel cell property, the collector-membraneassembly was removed, and the carbon woven-fabric was peeled from themembrane, and if the catalyst layer was connected to the carbonwoven-fabric or to the membrane was checked.

Tensile Test

This was measured at a test speed of 10 mm/min under 23° C. and arelative humidity of 50% according to Japan Industrial Standard (JIS K7127).

Reference Example 1

Synthesis of Aromatic Polymer Having Super Strong Acid Group In SideChain

Into a flask was charged 40 g of commercially availablepoly(oxy-4,4′-biphenyleneoxy-4,4′-diphenylsulfone) and 500 ml ofmethylene chloride, and to this mixture was added 37.4 g (210 mmol) ofN-bromosuccinimide, and 65.4 g of concentrated sulfuric acid was droppedover 30 minutes while keeping the temperature of the flask at 0° C. andstirring. After stirring for 4 hours at room temperature, the reactionsolution was poured into ice water, and 7.56 g (60 mmol) of Na₂SO₃ wasadded. Thereafter, an aqueous NaOH solution was added until pH reached10, then, methylene chloride was distilled under reduced pressure,filtrated and dried, to obtain 63.1 g of a polymer (a). Elementalanalysis, ¹H-NMR and ¹³C-NMR measurements were conducted to find that abromo group had been introduced into a phenyl ring of the resultedpolymer (a). The polymer (a) contained bromo groups introduced in anamount of 27 wt %. The molecular weight was measured by GPC measurementusing N,N-dimethylacetamide (hereinafter, referred to as DMAc) as adeveloping solvent, to find a number-average molecular weight of 34000based on a polystyrene calibration standard.

Into a flask was charged 15.01 g of5-iodo-octafluoropentyl-3-oxapentanesulfonyl fluoride, 5 ml of water, 5ml of methylene chloride, 4.80 g of 2,6-lutidine, and 0.1 ml of 1M THFsolution of tetra n-butyl ammonium fluoride, and they were allowed toreact for 4 days at room temperature. The reaction mixture was extractedwith methylene chloride three times, and the solvent was distilled underreduced pressure, then, 30 ml of THF and 2.82 g of potassium carbonatewere added to this and the mixture was stirred at room temperature for10 hours. The solid was filtrated, and the filtrate was concentrated tocause deposition of white solid. The white solid was re-crystallizedfrom a THF/toluene mixed solvent to obtain 12.3 g of white solid. Theresulted white solid was identified as potassium5-iodo-octafluoro-3-oxapentanesulfonate (b) by the results of ¹⁹F-NMR,and elemental analysis.

Into a flask of which air inside had been purged with nitrogen wascharged 0.500 g of the polymer (a), 0.500 g (7.87 mmol) of a copperpowder and 10 ml of dimethyl sulfoxide, and the mixture was stirred at120° C. for 2 hours. Then, 10 ml of a dimethyl sulfoxide solution of1.00 g (2.16 mmol) of the compound (b) was added while keeping at 120°C. They were reacted at 120° C for 40 hours, then, poured into 100 ml ofa 1N-HCl aqueous solution to precipitate a polymer. The precipitatedpolymer was dried to obtain an aromatic polymer (c) having a superstrong acid group in a side chain.

Reference Example 2

Synthesis of Sulfonated Aromatic Polymer

99 mg of anhydrous cupper chloride and 266 mg of 2-methylbenzoxazolewere stirred in 1 ml of toluene at room temperature under atmosphericpressure for 15 minutes. To this was added 8.5 g of 2-phenylphenol and30 ml of toluene, and the mixture was stirred at 50° C for 5 hours underan oxygen atmosphere. After completion of the reaction, the reactionsolution was poured into methanol acidified with hydrochloric acid toprecipitate a polymer which was filtrated and dried to obtainpoly(2-phenylphenylene ether) (hereinafter, referred to as PE1).

Into a flask equipped with an azeotropic distillation apparatus wascharged 3.0 g of SUMIKA EXCEL PES 5003 P (manufactured by SumitomoChemical Co., Ltd., polyether sulfone having hydroxyl group at the end),0.75 g of PE1, 0.04 g of potassium carbonate, 15 ml of DMAc and 3 ml oftoluene and the mixture was stirred with heating and dehydrated underazeotropic conditions of toluene and water, then, toluene was distilledoff. To this was added 0.05 g of 4,4′-difluorobenzophenone, and themixture was stirred for 5 hours while heating at 160° C. There actionsolution was dropped into large amount of methanol acidified withhydrochloric acid, the resulted precipitate was recovered by filtration,and dried under reduced pressure at 80° C to obtain 3.8 g of a blockcopolymer.

2 g of the resulted block copolymer was stirred together with 20 ml of98% sulfuric acid at room temperature, to give a uniform solution, then,the solution was stirred further for 2 hours. The resulted solution wasdropped into large amount of ice water, and the resulted precipitate wasrecovered by filtration. Further, mixer washing with ion-exchange waterwas repeated until the washing water became neutral, then, the mixturewas dried under reduced pressure at 40° C to obtain a sulfonatedaromatic polymer (d).

Reference Example 3

Production of Polymer Electrolyte Membrane by Complex Formation ofSulfonated Aromatic Polymer and Porous Membrane of Polyethylene Thepolymer (d) was dissolved at a concentration of 15 wt % in-DMAc, and thesolution was applied on a polyethylene porous membrane (membranethickness: 15 μm, void ratio: 48%, pore diameter: 0.05 μm) fixed on aglass plate. The solvent was dried at ambient pressure, to obtain acomplex membrane (e) of the sulfonated aromatic polymer and thepolyethylene porous membrane of polyethylene. The membrane thickness was27 μm.

Example 1

Production of Laminated Membrane using Spin Coater and Test of Fuel CellPerformance

The membrane (e) was cut into 4 cm square, and fixed on a glass plate ofa spin coater. While rotating the glass plate at 1000 rpm, 2 ml of amethylene chloride/methanol (15 vol %/85 vol%) solution (3 wt %) of theabove-mentioned polymer (c) was dropped onto the center of rotation overa period of 2 seconds to conduct spin coating. This was dried for 10minutes in a drier of 60° C, then, spin coating was conducted in thesame manner also on the remaining surface, to obtain the intendedlaminated membrane (f). The membrane thickness was 28 μm. The results ofevaluation of the properties of the membrane are shown in Table 1. Thefuel cell property test result showed cell voltage when current densitywas 0.50 (A/cm²).

Comparative Example 1

Fuel Cell Property Test of Membrane not Laminated

The property evaluation results of the membrane (e) are shown intable 1. The fuel cell property test result showed cell voltage whencurrent density was 0.50 (A/cm²).

TABLE 1 Result of evaluation of property of membrane Fuel cell propertyEvaluation of adhering evaluation property Example 1 0.58 V adhered toboth membrane and carbon woven fabric Comparative 0.48 V adhered only tocarbon example 1 woven fabric

By coating an aromatic polymer having a super strong acid group in aside chain on a surface layer of a polymer electrolyte membrane, anadhering property of the interface between a current collector and anelectrolyte membrane is improved, and the power generation property of afuel cell is improved.

Reference Example 4 (Production Example of Sulfonated Aromatic PolymerMembrane)

The polymer (d) was dissolved in a concentration of 15 wt % in DMAc, thesolution was cast and applied on a glass plate, and dried under ambientpressure to obtain a membrane (g) of a sulfonated aromatic polymer. Themembrane thickness was 27 μm.

Reference Example 5 (Production Example of Disulfonylimide)

At room temperature, into an ammonium chloride aqueous solution wasdropped an acetone solution of pentafluorobenzenesulfonyl chloride, andduring which, pH was regulated at 7 with an aqueous sodium hydroxidesolution. The precipitated product was filtrated, and re-crystallizedfrom toluene, to obtain pentafluorobenzenesulfoneamide. The structurewas confirmed by ¹H-NMR, ¹⁹F-NMR and IR.

To a tetrahydrofuran solution of pentafluorobenzenesulfoneamide wasadded NaH in 2-fold molar amount, subsequently,pentafluorobenzenesulfonyl chloride of equi-molar amount was addedslowly, and they were reacted at 60° C. The reaction mass was filtrated,then, the filtrate was concentrated and dissolved in methanol and tothis was added a KOH methanol solution, to obtain the intended potassiumsalt of disulfonylimide (h). It was purified by re-crystallization froman acetone-methanol mixed solvent. ¹⁹F-NMR (ppm): −130, −142, −154 .

Reference Example 6 (Alternating Copolymer Composed of (h) andHydroquinone)

Into a flask was charged, under a nitrogen flow, 2.58 g of the salt (h),0.551 g of hydroquinone, 0.795 g of potassium carbonate and 12 ml ofdimethyl sulfoxide and they were stirred while heating for 19 hours at80° C. After completion of the reaction, the reaction solution wasdropped into a 10% hydrochloric acid methanol solution, the resultedprecipitate was recovered by filtration and washed with methanol, then,dried under reduced pressure at 60° C. 3.00 g of a disulfonylimidepolymer (i) was obtained as brown solid.

Example 2

Production of Laminated Membrane using Spin Coater and Test of Fuel CellProperty

The membrane (g) obtained by Reference Example 4 was cut into 4 cmsquare, and fixed on a glass plate of a spin coater. While rotating theglass plate, 2 ml of a methylene chloride/methanol (15 vol %/85 vol%)solution (3 wt %) of the above-mentioned polymer (i) was dropped ontothe center of rotation over a period of 2 seconds toconduct spincoating. This was dried for 10 minutes at 60° C, then, spin coating wasconducted in the same manner also on the remaining surface, to obtainthe intended laminated membrane (j). The membrane thickness was 29 μm.The results of evaluation of the properties of the membrane are shown inTable 2. The fuel cell property test result showed cell voltage whencurrent density was 0.50 (A/cm²).

Comparative Example 2

Fuel Cell Property Test of Membrane not Laminated

The property evaluation results of the membrane (g) are shown in table2. The fuel cell property test result showed cell voltage when currentdensity was 0.50 (A/cm²).

TABLE 2 Result of evaluation of property of membrane Fuel cell propertyEvaluation of adhering evaluation property Example 2 0.67 V adhered toboth membrane and carbon woven fabric Comparative 0.59 V adhered only tocarbon example 2 woven fabric

By coating a polymer having a polymer unit of the above-mentionedformula (4) in a main chain on a surface layer of a polymer electrolytemembrane, an adhering property of the interface between a currentcollector and an electrolyte membrane is improved, and the powergeneration property of a fuel cell is improved.

Reference Example 7

Into a flask was charged under nitrogen 55.9 g (300 mmol) of4,4′-dihydroxybiphenyl, 66.1 g (280 mmol) of m-dibromobenzene and 200 gof benzophenone and the mixture was heated at 100° C. The mixture wasuniform. Further, 44.2 g of potassium carbonate and 60 mol of toluenewere added to this and stirred, water generated was removed byazeotropic dehydration with toluene, and toluene was further removed. Tothis was added 143 mg of copper bromide (I), and the flask was heated at200° C to carry a reaction for 6 hours. After reaction, the reactionsolution was put into methanol to obtain 36 g of the precipitatedpolymer (k). The yield was 48%.

Then, into a flask were charged 72.0 g of SUMIKA EXCEL PES 5003 P(manufactured by Sumitomo Chemical Co., Ltd., polyether sulfone havinghydroxyl group at the end) and 24.0 g of the above-mentioned polymer(k), and dissolved in 480 ml of DMAc while stirring. Further, 2.52 g ofpotassium carbonate and 4.81 g of decafluorobiphenyl were added andreacted at 80° C. for 4 hours, at 100° C for 2 hours and at 110° C for 1hour. Thereafter, the reaction solution was dropped into large amount ofmethanol acidified with hydrochloric acid, the precipitate insoluble inmethanol was recovered by filtrated, and dried under reduced pressure at80° C to obtain 96 g of a block copolymer (1).

90 g of the resulted block copolymer (1) was dissolved in 450 ml ofconcentrated sulfuric acid and reacted at 60° C for 3 days, then, thereaction solution was poured into large amount of ice water, and theresulted precipitate was recovered by filtration. Further, washing withion-exchange water was repeated until the washing liquid became neutral,then, dried under reduced pressure at 40° C to obtain a sulfonatedaromatic polymer (m).

The polymer (m) was dissolved in DMAc to prepare a 15 wt % solution. Thesolution was applied on a glass plate, and dried at 80° C to obtained amembrane (n) of a sulfonated aromatic polymer. The thickness of themembrane (n) was 47 pin. As a result of measurement of the molecularweight by GPC measurement using DMAc as a developing solvent, thenumber-average molecular weight was 56000 based on a polystyrenecalibration standard. The number of mole of sulfonic groups per unitweight (ion exchange capacity) of the resulted polymer was 1.62 meq/g.

Example 3

The membrane (n) was cut into 4 cm square, and fixed on a glass plate ofa spin coater. While rotating the glass plate at 1000 rpm, a 5 wt %alcohol/aqueous solution (manufactured by Aldrich) of Nafion was droppedonto the center of rotation over a period of 2 seconds to conduct spincoating, and dried at 60° C. The same spin coat operation was repeatedthree times on the same surface. Then, spin coating was conducted in thesame manner also on the opposite surface, to obtain the intendedlaminated membrane (p). The thickness of the membrane (p) was 53 μm. Theresults of evaluation of the properties of the membrane are shown inTable 3.

Example 4

The same procedure as in Example 1 was conducted except that a solutionprepared by adding 4 g of methylene chloride to 3 g of 5 wt %alcohol/aqueous solution of Nafion was used and spin coating wasrepeated eight times on one side, to obtain a laminated membrane (q).The thickness of the membrane (q) was 55 μm. The results of evaluationof the properties of the membrane are shown in Table 3.

Comparative Example 3

The results of evaluation of the properties of the membrane (n) areshown in Table 3.

Comparative Example 4

The results of evaluation of the properties of a Nafion membrane(thickness: 50 μm) manufactured by Aldrich are shown in Table 3.

TABLE 3 Fuel cell property evaluation Cell voltage Current when currentdensity when density is cell voltage is Evaluation of 0.50 A/cm² 0.20 Vadhering property Example 3 0.68 V 1.96 A/cm² adhered to both membraneand carbon woven fabric Example 4 0.68 V 1.80 A/cm² adhered to bothmembrane and carbon woven fabric Comparative 0.61 V 1.38 A/cm² adheredonly to example 3 carbon woven fabric Comparative 0.65 V 1.38 A/cm²adhered to both example 4 membrane and carbon woven fabric

Example 5, Comparative Example 5

The tensile test was conducted on the membrane (q) and the same Nafionmembrane (thickness: 50 μm) as described above. The elastic modulus ofthe membrane and stress at breakage of the membrane are shown in Table4.

TABLE 4 Result of tensile test Elastic modulus Stress at breakage (MPa)(MPa) Example 5 720 26 Comparative example 5 186 20

The above-mentioned examples and comparative examples show that alaminated membrane comprising a perfluoroalkylsulfonic acid polymermembrane and non-perfluoroalkylsulfonic acid polymer electrolytemembrane shows improved adhering property of the interface between acurrent collector and an electrolyte membrane and manifests improvedpower generation property of a fuel cell. Further, when compared with aperfluoroalkylsulfonic acid polymer, this laminated membrane has alsoexcellent mechanical properties such as high elastic modulus, highstress at breakage and the like.

INDUSTRIAL APPLICABILITY

The laminated membrane of the present invention is an electrolytemembrane excellent in power generation property and also excellent inmechanical strength.

1. A laminated membrane comprising a membrane (I) which comprisesaromatic polymer electrolyte containing a super strong acid group and amembrane (II) which comprises one electrolyte selected from the groupconsisting of perfluoroalkylsulfonic acid polymer electrolytes andnon-super strong acid polymer electrolytes.
 2. The laminated membraneaccording to claim 1, wherein aromatic polymer electrolyte containingthe super strong acid group is represented by the following generalformula (1):-(A-Z)_(m)-(A′-Z′)_(n)-  (1) (wherein, A represents a divalent aromaticgroup and A′ represents a divalent aromatic group on which super strongacid group has been substituted. Z, Z′ represent each independently adirect bond or divalent group. m, n represent the number of repeatingunits, n is in the range of 10 to 100000, n repeating units may be thesame as or different from each other, and m is in the range of 0 to100000, m repeating units may be the same as or different from eachother.
 3. The laminated membrane according to claim 2, wherein Arepresents a divalent aromatic group selected from the following generalformulae (3a) to (3c), and A′ represents a divalent aromatic groupselected from the following general formulae (3d) to (3g):

wherein, R represents a hydroxyl group, alkyl group having 1 to 6 carbonatoms, alkoxy group having 1 to 6 carbon atoms, alkyl group having 7 to12 carbon atoms, aryl group or halogen. p, r, s and t represent eachindependently a number of from 0 to 4, and q represents a number of from0 to 6, and when there are a plurality of Rs, these may be the same ordifferent. j represents a number of 0 or
 1. Y represent a direct bond ordivalent group, and when there are a plurality of Ys, these may be thesame or different. Z″ and Y represent each independently a direct bondor divalent group, and when there are a plurality of Z″s, these may bethe same or different, and D represents a super strong acid group, andwhen there are a plurality of Ds, these may be the same or different. h,h″ and h′″ represent each independently a number of from 1 to 4, h′represents a number of from 1 to 6, (p′+h), (r′+h″) and (s″+h′″)represent each independently a number of from 1 to 4, s′, t′, r″ and t″represent each independently a number of from 0 to 4, (q′+h′) representsa number of from 1 to 6, and j represents a number of 0 or
 1. 4. Thelaminated membrane according to claim 3, wherein Z, Z′ and Y representeach independently a group selected from a direct bond, —O—, —S—, —CO—,—SO₂—, alkylene groups having 1 to 20 carbon atoms and alkylenedioxygroups having 1 to 20 carbon atoms, and Z″ represents a group selectedfrom the group consisting of a direct bond, —O—, —S—, —CO—, —SO₂—,alkylene groups having 1 to 20 carbon atoms optionally substituted withfluorine, alkylenedioxy groups having 1 to 20 carbon atoms optionallysubstituted with fluorine, arylene groups having 6 to 12 carbon atomsoptionally substituted with fluorine, aryleneoxy groups having 6 to 12carbon atoms optionally substituted with fluorine and alkyleneoxy groupshaving 1 to 20 carbon atoms optionally substituted with fluorine.
 5. Thelaminated membrane according to claim 2, wherein the super strong acidgroup is selected from group of the following general formulae (2a) to(2d):-G-SO₃ ^(−W) ⁺  (2a)-G-SO₂N⁻W⁺SO₂-E   (2b)-G-P(O)(O⁻W⁺)₂   (2c)-G-P(O)O⁻W⁺-E   (2d) (wherein, G represents an alkylene group of whichhydrogen atoms are partially or totally substituted with fluorine,aralkylene group of which hydrogen atoms are partially or totallysubstituted with fluorine or arylene group of which hydrogen atoms arepartially or totally substituted with fluorine, W⁺ represents a cation,E represents an alkyl group of which hydrogen atoms are partially ortotally substituted with fluorine, aralkyl group of which hydrogen atomsare partially or totally substituted with fluorine or aryl group ofwhich hydrogen atoms are partially or totally substituted with fluorine.6. The laminated membrane according to claim 5, wherein W represents ahydrogen ion.
 7. The laminated membrane according to claim 1, whereinaromatic polymer electrolyte containing the super strong acid group is apolymer having a polymerization unit of the following formula (4):—[Ar¹—(SO₂—N⁻(X⁺)—SO₂—Ar²)_(a)—SO₂—N⁻(X⁺)—SO₂—Ar¹—O]—  (4) (wherein,Ar¹, Ar² represent each independently a divalent aromatic groupoptionally having a substituent, a represents an integer of 0 to 3, andX⁺ represents an ion selected from a hydrogen ion, alkali metal ions andammonium.
 8. The laminated membrane according to claim 7, whereinaromatic polymer electrolyte containing the super strong acid group is apolymer further having a repeating unit of the following formula (5)—[Ar³—O]—  (5) (wherein, Ar³ represents a divalent aromatic groupoptionally having a substituent.) in its main chain.
 9. The laminatedmembrane according to claim 8, wherein aromatic polymer electrolytecontaining the super strong acid group is a polymer further having arepeating unit of the following formula (6)—[Ar⁴—O]—  (6) (wherein, Ar⁴ represents a divalent aromatic groupoptionally having a substituent in its main chain.
 10. The laminatedmembrane according to claim 7, wherein the divalent aromatic groupoptionally having a substituent is at least one selected from thefollowing aromatic groups:

(wherein, R¹ represents a hydrocarbon group having 1 to 10 carbon atoms,hydrocarbonoxy group having 1 to 10 carbon atoms, acetyl group, benzoylgroup, nitrile group, sulfonic group, carboxyl group, phosphonic groupor halogen atom, a represents an integer of from 0 to 4, and b, crepresent-an integer of from o to 4, the sum of b and c is being from 0to
 6. When there are a plurality of R¹s, these may be the same ordifferent. Y represents a direct bond, —O—, —S—, —C(O)—, —SO2— or—C(R³)₂—, R³ represents a hydrogen atom, hydrocarbon group having 1 to10 carbon atoms, halogenated hydrocarbon group having 1 to 10 carbonatoms, and two R³S may be the same or different and may form a ring.When there is a plurality of Ys, these may be the same or different. 11.The laminated membrane according to claim 7, wherein Ar¹ representstetrafluorophenylene.
 12. The laminated membrane according to claim 7,wherein a represents 0 or
 1. 13. The laminated membrane according toclaim 7, wherein aromatic polymer electrolyte containing the superstrong acid group is a block copolymer having at least one block havinga repeating unit of the formula (4) and a repeating unit of the formula(5).
 14. The laminated membrane according to claim 7, wherein X⁺represents a hydrogen ion.
 15. The laminated membrane according to claim1, wherein the non-super strong acid polymer electrolyte is an aromaticpolymer electrolyte.
 16. The laminated membrane according to claim 1,wherein the membrane (II) is the surface layer on at least one surface.17. The laminated membrane according to claim 1, wherein the proportionof the membrane (II) in the laminated membrane is 0.1 wt % to 50 wt %.18. A fuel cell comprising the laminated membrane according to claim 1.19. The fuel cell according to claim 18, wherein a mixture of carboncarrying a catalyst and perfluoroalkylsulfonic acid resin fixed on anelectrode is used as a current collector.